Within the power industry, valves are operated remotely from open, closed and intermediate positions to improve or maintain utility power plant output, or in many cases to provide for the protection of the general public from release of radioactive materials either directly or indirectly. Continual, proper operation of these valves is essential to the well-being of the industry and the general public. The extreme emphasis on safety in nuclear power plants (and the presently bad reputation of the nuclear industry) has put a premium on the importance of maintaining proper operation of valves, of which there may be hundreds within a single plant.
At the forefront of industry attempts to monitor and maintain proper operation of these critical valves is the recent invention of Arthur G. Charbonneau, et al described in U.S. Pat. No. 4,542,649 (herein referred to as "649"). The 649 invention disclosed a new and important valve operator monitoring system to measure, record and correlate valve stem load, limit and torque switch positions, spring pack movement and motor current, providing time related information on valve performance. The information made available by the 649 patent provides a direct indication of developing valve and operator problems, such as excessive or inadequate packing load, excessive inertia, proximity to premature tripping, incorrectly set operating limit and torque switches, improperly functioning thermal overload devices, inadequate or excessive stem thrust loads, gear train wear, stem damage, and load relaxation.
Specifically, the "649" invention accomplishes monitoring of valve operator parameters by direct signal and equipment measurements taken at the location of the valve or valve operator. A user must venture to the location of the valve/valve operator and take direct measurements for monitoring purposes. More and more demand is being made by government and other agencies for a system which can monitor a valve condition from a remote, meaning distant, location, i.e. the power plant operation center or Master Control Center. Neither the "649" invention nor other known prior art provides a reliable system for accomplishing such remote monitoring.
Moreover, prior art valve monitoring is typically accomplished during no-flow conditions and requires at least minor, temporary modification of the valve operator. In nuclear power plants, if not also other facilities, testing equipment which is intrusive, meaning it in anyway modifies the valve operator or its circuitry, can not be left connected during valve-in-use conditions. Thus, typical prior art monitoring and testing is under no flow conditions with operation of the plant or valve sector closed down. Thus, a need exists for nonintrusive (and, thus, "remote") systems for monitoring the condition of the valve operator during actual valve-in-use conditions to signal the need for more extensive testing or maintenance of the valve or valve operator.